I have a Yanmar 3QM30F engine on my sailboat. Forward gear is slipping. The transmission is ratio 2.03. Have been offered a ratio 3.01 transmission but was told the engine was not powerful enough for the 3.01 transmission. What am I missing here? Seems to me that the propeller will now go about 50% faster for the same revs as the 2.03 ratio transmission. Am I right or what? Will the 3.01 ratio be faster or slower?

ron_cairns

11-01-2007, 06:58 PM

"There are 2 clutch packs and they are cinter and steel plates. 1 pack for forward &amp; another for reverse. You will have to change these packs. Best to do both as they give you the overall dimentions for the specs to be able to shift from forward &amp; reverse. The 3.01 ratio is not that common, stick with the 2.03 ratio. The 3.01 will give you a slower turn and you would need a larger prop. ie each 3.01 turns of the engine will give 1 turn on the prop shaft. Example, speed boats like Miss Budwiser would use a 1:1 ratio. A large fish boat would use a 5:1 ratio.
This gear is made under licence from Hurth Gear, which is now owned by ZF. The clutch packs are the same but all else is to Yanmar specs.
Hope this is of some help. Ron"

davimack

11-01-2007, 09:17 PM

"Thank you so much for your concise and extremely helpful response. Now I understand!! Will try to
obtain the new clutch packs, and rebuild the unit. Is it a difficult job, or basically just logical ??!!
Will try getting the clutch packs from Hurth, and go from there. Any good suppliers you know of??
Thank you again for your help."